Time-Resolved Energy Spread Studies at the ANKA...

0 2017/05/15 Benjamin Kehrer - Time-resolved energy spread studies at theANKA storage ring

Institute for Beam Physics and Technology (IBPT)

Time-resolved energy spread studies at theANKA storage ring

Benjamin Kehrer, E. Blomley, M. Brosi, E. Bründermann, N. HillerA.-S. Müller, M. Nasse, P. Schütze, J. L. Steinmann, M. SchedlerM. Schuh, P. Schönfeldt, M. Schwarz, N. Smale

KIT – The Research University in the Helmholtz Association www.kit.edu

Project is funded by the FederalMinistry of Education and Researchunder contract number 05K16VKA

Outline

Introduction

Setup and DAQFast-gated intensified camera (FGC)Schottky diodes + DAQ

Synchronous measurements

Short bunch-length bursting

Summary and outlook

Micro-bunching instabilities

Self-interaction of bunch with its own field

Deformation of longitudinal phase spaceOccurs above the bursting thresholdCSR emission (THz range) in bursts

Self-interaction of bunch with its own fieldDeformation of longitudinal phase space

Occurs above the bursting thresholdCSR emission (THz range) in bursts

−5 0 5Position (σz, 0)

gy (σ

Self-interaction of bunch with its own fieldDeformation of longitudinal phase spaceOccurs above the bursting threshold

CSR emission (THz range) in bursts

gy (σ

Self-interaction of bunch with its own fieldDeformation of longitudinal phase spaceOccurs above the bursting thresholdCSR emission (THz range) in bursts

gy (σ

0 2 4 6 8Time (ms)

Examples of previous studies

MeasurementsEnergy spread above bursting threshold→ Increases with bunch current1

Energy spread and microwave radiation→ Same modulation period length

Simulation: Bunch length and CSR→ Same modulation period length

Idea: Time-resolved energy spread studies with single-turn resolutionand benchmark against CSR

1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).

Energy spread and microwave radiation→ Same modulation period length2

Simulation: Bunch length and CSR→ Same modulation period length

1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).

Simulation: Bunch length and CSR→ Same modulation period length3

1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).3R. Warnock et al., Nucl. Instrum. Meth. A561, 186 (2006).

Simulation: Bunch length and CSR→ Same modulation period length3

1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).3R. Warnock et al., Nucl. Instrum. Meth. A561, 186 (2006).

Synchrotron light source at KITCircumference: 110.4 mBunch spacing: 2 nsRegular low-αc runs→ Short bunchesStudies of micro-bunchinginstabilities

Measurement principle

Energy spread σδMeasure the horizontal bunch size σx in dispersive section of storage ring

σδ =1

√σ2

x −βx · εx

Single turn base?→ Use a fast-gated intensified camera

Fast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

Synchronisation

Hardware synchronisation schemeTriggered beam based calibration

σδ =1

√σ2

x −βx · εx

CSRFast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

Synchronisation

Hardware synchronisation schemeTriggered beam based calibration

M. Brosi, THOBA1

σδ =1

√σ2

x −βx · εx

CSRFast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

SynchronisationHardware synchronisation scheme4

Triggered beam based calibration

M. Brosi, THOBA1

4B. Kehrer et al.; IPAC’16 (MOPMB014).

Fast-gated intensified camera (FGC)

Setup at visible light diagnostics beamline5,6

Based on previous works of J. Corbett, W. Cheng7 and A. Fisher8

5P. Schuetze et al., IPAC’15 (MOPHA039).6B. Kehrer et al., IPAC’15 (MOPHA037).7W. Cheng et al., PAC’09 (TH6REP032).8A. Fisher et al., AIP Conference Proceedings (Vol. 868, No. 1, pp. 303-312).

CameraAndor iStar 340TGate width: 1.55 ns FWHMGate separation: > 6 turns (500 kHz)

Mirror7 mm apertureGalvo drive

Drawback: compromise betweenresolution and time rangeIdeal: Continuous turn-by-turn data

FGC: Data analysis

FGC raw image

Determine spot size → 2D Gaussian fitsTiming calibration

FGC: Data analysis

FGC raw imageDetermine spot size → 2D Gaussian fits

Timing calibration

FGC: Data analysis

FGC raw imageDetermine spot size → 2D Gaussian fits

Timing calibration

Raw data 2D fit

FGC: Data analysis

FGC raw imageDetermine spot size → 2D Gaussian fitsTiming calibration

Raw data 2D fit

FGC: Data analysis

FGC raw imageDetermine spot size → 2D Gaussian fitsTiming calibration

Raw data 2D fit

Schottky diodes + KAPTURE

Required: CSR intensity once per bunch and turn

Detectors: Schottky barrier diodes

Room temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTURE

In-house developed DAQ system9

4 ADC with turn-by-turn and bunch-by-bunch capability (sampling with fixedphase)Continuous streaming

9M. Caselle et al., Journal of Instrumentation 12, C01040 (2017).

Detectors: Schottky barrier diodesRoom temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTURE

In-house developed DAQ system9

Detectors: Schottky barrier diodesRoom temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTUREIn-house developed DAQ system9

Horizontal bunch size and CSR: Example I

0 2 4 6 8Time (ms)

7580859095

0 2 4 6 8Time (ms)

100150200250300

0 2 4 6 8Time (ms)

7580859095

0 2 4 6 8Time (ms)

100150200250300

Energy spread with same modulation pattern as CSR

0 2 4 6 8Time (ms)

7580859095

0 2 4 6 8Time (ms)

100150200250300

Energy spread with same modulation pattern as CSR

Energy spread rises

at onset of burst

Horizontal bunch size and CSR: Example II

0 2 4 6 8Time (ms)

70727476788082

0 2 4 6 8Time (ms)

70727476788082

0 2 4 6 8Time (ms)

Energy spread decreases

0 2 4 6 8Time (ms)

70727476788082

0 2 4 6 8Time (ms)

CSR increases

0 2 4 6 8Time (ms)

70727476788082

0 2 4 6 8Time (ms)

CSR increases

Energy spread

reaches limit

0 2 4 6 8Time (ms)

70727476788082

0 2 4 6 8Time (ms)

CSR increases

Energy spread

reaches limit

Onset of next burst

Horizontal bunch size and CSR: Example III

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

Study in more detail → 24 turns gate separation, 500 µs time range

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

CSR negligible

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

CSR negligible

CSR starts to increase→ sub-structures

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

CSR negligible

Sub-structures too small

to increase bunch size

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

CSR negligible

Minimum energy spread

0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

0.0 0.1 0.2 0.3 0.4Time (ms)

CSR negligible

Minimum energy spread

Onset of next burst

Bursting threshold

0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

Bursting thresholdMean spot size

Bursting threshold

0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

Microbunching instabilities→ Energy spread increase

Bursting threshold

0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

Energy spread

constant

Bursting threshold

0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

Energy spread

constant

But: Not always the case

“Short bunch-length bursting”

Simulations predicted weak instability below the bursting threshold10

Measured on CSR at ANKA11 for αc ≤ 2.64 · 10−4

Instability would lead to energy spread increase

10K. Bane et al., Phys. Rev. ST Accel. Beams 13, 104402 (2010).11M. Brosi et al., IPAC’16 (TUPOR006).

Bursting threshold

Short bunch-

length bursting

Bursting threshold

Short bunch-

length bursting

0.1 0.3 0.5 0.7Bunch current (mA)

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Bunch current (mA)

16 ≤ Ib ≤ 40µA

Energy spread

increase

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

16 ≤ Ib ≤ 40µA

Energy spread

increase

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

16 ≤ Ib ≤ 40µA

Energy spread

increase

Coincides with

CSR increase

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

16 ≤ Ib ≤ 40µA

Energy spread

increase

Coincides with

CSR increase

→ Signature of short-bunch length bursting

Acknowledgements

KIT THz-Team (from IBPT, IMS, IPE, IPS and LAS):M. Balzer, E. Blomley, T. Boltz, A. Borysenko, M. Brosi, E. Bründermann,M. Caselle, C. Chang*, N. Hiller, S. Höninger, M. Hofherr, E. Huttel, K.S. Ilin,V. Judin*, M. Klein*, S. Marsching, Y.-L. Mathis, M.J. Nasse, G. Niehues,A. Plech, J. Raasch, P. Rieger*, L. Rota, R. Ruprecht, M. Schedler,A. Scheuring, P. Schönfeldt, M. Schuh, P. Schütze*, M. Schwarz, M. Siegel,N.J. Smale, B. Smit, J. Steinmann, P. Thoma*, M. Weber, S. Wuensch, M. Yan,and A.-S. Müller*THz-Alumni

For interesting discussions, good ideas and a lot of fun:F. Caspers (CERN), S. Khan (DELTA), P. Peier, B. Steffen (DESY),H.-W. Hübers, A. Semenov (DLR), P. Kuske, G. Wüstefeld (HZB),V. Schlott (PSI) ,Y. Cai, J. Corbett, R. Warnock (SLAC), S. Bielawski, C. Evain,E. Roussel, C. Szwaj (U. Lille)

Summary

Fast-gated intensified camera versatile setup for energy spreadstudies

Synchronous measurementsCoherent synchrotron radiation (CSR)Horizontal bunch size → energy spread

For certain beam currents and machine parameters→ Energy spread with same modulation frequency as CSR burstsShort bunch-length bursting (weak instability)→ Energy spread increase

Next stepsContinuous sampling and data streamingFor CSR already possible (KAPTURE)Using a 256-pixel line array for turn-by-turn sampling of a single bunchLongitudinal bunch profile: Electro-Optical Spectral DecodingHorizontal bunch profile: Replace FGC to overcome resolution limit

Summary

Fast-gated intensified camera versatile setup for energy spreadstudiesSynchronous measurements

Coherent synchrotron radiation (CSR)Horizontal bunch size → energy spread

Summary

For certain beam currents and machine parameters→ Energy spread with same modulation frequency as CSR bursts

Short bunch-length bursting (weak instability)→ Energy spread increase

Summary

Thank you for your attention!

Horizontal planeCourtesy Paul Schütze

Time-Resolved Energy Spread Studies at the ANKA...

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